1. Field of the Invention
The invention relates to a cooling structure of a cylinder block, and more particularly to a cooling structure of a cylinder block, which makes it possible to uniformly cool the cylinder block.
2. Description of the Related Art
A conventional cooling structure of a cylinder block is disclosed, for example, in Japanese Patent Laid-Open Publication No. 2002-30989.
In the conventional cooling structure of a cylinder block disclosed in the Japanese Patent Laid-Open Publication No. 2002-30989, a temperature of a bore wall is made uniform in a circumferential direction of a bore by inserting a water jacket spacer which is separate from a cylinder block in a water jacket of the cylinder block.
However, in the conventional cooling structure of a cylinder block, an inter-bore region which is positioned in the vicinity of a boundary between bore regions adjacent to each other is not sufficiently cooled. This is thought to be because the flowing coolant has inertia, and therefore the coolant is not supplied to a sharply constricted portion between the bore regions at a sufficient flow rate, and the coolant stagnates in the inter-bore region. Also, since a cross sectional area of a passage in the inter-bore region is large, a flow speed of the coolant is reduced in the inter-bore region, and therefore the inter-bore region is not sufficiently cooled. That is, since the coolant is not supplied to the sharply constricted portion between the bore regions at a sufficient flow rate, the portion is not sufficiently cooled.